4s 12v configuration

shadowsteve

Solar Enthusiast
I'm building two 12v banks using 280ah cells in a 4s setup each with a JBD BMS.

The BMS is longer than the batteries if I use the bus bars and put them face to face (right side of pic) and clamp as normal.

If I put them in pairs and put a clamping rod in the center then the pack suits the BMS length better and ends up a bit narrower (left side of pic). I will make cables to go where the masking tape shows connections.

Any issues with the second setup that I might have missed? I couldn't find any pics of this arrangement although I'm sure they are out there
 

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MisterSandals

Participation Medalist
Your pic looks like you have the + of one battery (connected to the BMS C-) and the - of the other battery (connected to the BMS B-).
That looks really wrong.
 

shadowsteve

Solar Enthusiast
Your pic looks like you have the + of one battery (connected to the BMS C-) and the - of the other battery (connected to the BMS B-).
That looks really wrong.
BMS isn't connected to anything in the pic. I just replaced the pic as one of the left side batteries was reversed.

When I had the BMS connected to the right side pack I had batt- to B- and C- was negative out
 

100 Proof

"Please Lord, don't let me do something stupid."
Your pic looks like you have the + of one battery (connected to the BMS C-) and the - of the other battery (connected to the BMS B-).
That looks really wrong.
I tlooks like only one battery is wired to the BMS, but not to the correct place. The other battery has tape only on it. BTW, my comment was about his buss bar arrangement.
 

shadowsteve

Solar Enthusiast
So I had the right side block wired up to check the BMS connectivity. The fuse block is being used as "+/-" termination points so that the wires don't shift on the bench and touch. The end of wire that is off the edge of the table was connected to the "-" terminal on the lower left corner of the right side block.

The block on the left side has masking tape to indicated where wires goes. Using wire for interconnects removes any stress on the terminals. The masking tape is not rated for 150A so I will replace it.
 

100 Proof

"Please Lord, don't let me do something stupid."
So I had the right side block wired up to check the BMS connectivity. The fuse block is being used as "+/-" termination points so that the wires don't shift on the bench and touch. The end of wire that is off the edge of the table was connected to the "-" terminal on the lower left corner of the right side block.

The block on the left side has masking tape to indicated where wires goes. Using wire for interconnects removes any stress on the terminals. The masking tape is not rated for 150A so I will replace it.
The ONLY thing that should be connected to the BMS from the + battery terminal is the sense wire (the small red wire you have connected). The white + battery wire does NOT connect anywhere else on the BMS, even thru a fuse or terminal block.
 

shadowsteve

Solar Enthusiast
The ONLY thing that should be connected to the BMS from the + battery terminal is the sense wire (the small red wire you have connected). The white + battery wire does NOT connect anywhere else on the BMS, even thru a fuse or terminal block.
I never said it did. In the picture it isn't connected to the BMS either. There is NO fuse in the picture. There's a terminal block only. The BMS is connected to the terminal block and if I put the wire back onto the battery and plugged back in the balance connector it would be functional.
 

100 Proof

"Please Lord, don't let me do something stupid."
I think I see the problem. The skech they furnish is a little confusing. That thing in the red oval LOOKS like a fuse or a terminal block, but it is meant to represent your downstream devices like your SCC, inverter, etc.

As long as your terminal block does NOT have continuity thru it you should be good. I assumed, wrongfully I hope, that it had continuity between the 2 terminals.
 

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shadowsteve

Solar Enthusiast
View attachment 62425
View attachment 62426
View attachment 62427
Battery + to terminal block to C-. Not going to end well.
The only way it doesn't end well is if I put a fuse between the two posts and then I have a blown fuse. The wires I used are only to test the BMS setup. They're light gauge wires pulled from wire harness bin.

The black terminal block is two separate posts that are installed into a plastic base. There is no interconnection between the two posts nor do I ever intend to make a connection as those two posts are the positive and negative battery terminals and I prefer not to let anything conductive come between them. Would it be easier to see if I'd just left two bare wire ends laying on the table?

I started the thread to ask about the physical/electrical configuration of the cells and only left the BMS in the picture to illustrate that it is longer than the right block and hence causes packaging issues.
 

shadowsteve

Solar Enthusiast
I think I see the problem. The skech they furnish is a little confusing. That thing in the red oval LOOKS like a fuse or a terminal block, but it is meant to represent your downstream devices like your SCC, inverter, etc.
They actually show the B+ connected to the battery + but I didn't do that. Your picture is an older BMS version too. If you just ignore all of the wiring on the BMS and the terminal block then I can just get back to the battery physical config which I'll assume is fine seeing as nobody commented on the compression or anything which is what I was looking for.
 

MisterSandals

Participation Medalist
Sure, you just confused the situation. If I could delete a thread I would :rolleyes:
When you get your replacement BMS, you can start a new thread.
Seriously, @100 Proof was spot on in is assessment: that is NOT a terminal block that is circled in his pic, it represents the output (both + and -) from a charge controller.
 

shadowsteve

Solar Enthusiast
Just to simplify it I reconnected everything and took the other pack out of the picture. Four balance wires connected (bc0 isn't used), B- to battery-, C- to power bank negative, battery+ to power bank positive. Meter is showing the 13.20v power bank output from the two OUTPUT terminals which you may have confused with a fuse holder as it would be in another situation.

I also attached a picture of the BMS data 😁
 

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MisterSandals

Participation Medalist
two OUTPUT terminals which you may have confused with a fuse holder as it would be in another situation.
Ah, i was thinking along the lines of a bus bar, not 2 distinct terminals.
And your BMS is only using the sensing wires to run, and those looked fine from the get go.

So glad its all good. Just trying to help.

You can hit the "Report" button and see if an admin will clean up this thread or maybe even delete it.
 
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